1. Field of the Invention
This invention relates to vehicle seat headrests having side portions that move in response to a side impact in a forward direction to provide lateral support for a seat occupant""s head.
2. Background Art
Vehicle seats have head restraints that are generally provided for the purpose of protecting against front and rear impacts. Whether active or passive, prior art head restraints offer little protection in the event of a side impact. While the most common type of vehicle collisions are front and rear, side impacts and impacts that are combination side and front or rear (diagonal) impacts are also well known. Recently, side air curtains have been developed and are currently being implemented in new vehicles. While side air curtains may be beneficial in severe collisions, they are normally set to deploy in only relatively severe side impacts. Side air curtains also must travel approximately one foot between the side of the interior of the vehicle and the head of a passenger. Side air curtains must also deploy around the side of a vehicle seat that may be in a range of locations fore and aft in the vehicle.
Prior art headrests have been developed that include positionable or fixed wings on the sides of headrests. An example of one such system is disclosed in U.S. Pat. No. 6,123,389 that includes a fixed or manually positionable wing member that are attached to a back member.
Another approach to providing side support for a seat is disclosed in U.S. Pat. No. 4,205,878 that discloses a telescopic headrest member that is attached to either side of a backrest.
Another prior art headrest design is disclosed in U.S. Pat. No. 4,883,243 that discloses a headrest having a front wall that may be retracted toward a rear wall thereby allowing a pilot""s head to be received between two rigid side walls of an ejection seat.
Another approach disclosed in U.S. Pat. No. 5,496,061 and U.S. Pat. No. 5,505,487 is to provide a side impact air bag module that is deployed from a headrest. The air bag module is normally retained in a cavity formed in the side of the headrest. The air bag is deployed by an inflator that drives the air bag module on a pair of guide rods to a position outboard of the headrest where upon the air bag may be deployed in the forward direction.
Static headrests with forwardly extending wing portions suffer from the disadvantage of confining a seat occupant""s head at all times that can potentially impede visibility and may also make the vehicle occupant feel confined. Manually adjustable headrests are also generally passive devices that a user may defeat the purpose of by not positioning the side wings to extend forwardly. If the side wings are positioned to extend forwardly, they suffer from the same disadvantage of being confining and potentially blocking visibility described above.
Dynamic headrest devices such as the retractable front wall or air bag types of devices suffer from the disadvantage of being complex and expensive. Electronic controls, sensors, and actuators must be used to control these types of devices in the event of an impact.
These and other drawbacks and disadvantages associated with prior art headrests are addressed by applicant""s invention as summarized below.
According to one aspect of the present invention, a vehicle headrest assembly is provided that includes a headrest pad having a front surface wherein at least one side portion of the headrest pad has a first position but that is shiftable in a forward direction to a second position forward of the front surface of the headrest pad. A shift mechanism is provided for moving the side portion from the first position to the second position. A trigger is provided that is actuated in response to an impact that causes the shift mechanism to move the side portion from the first position to the second position.
According to another aspect of the invention, the headrest pad may have a central section that is flanked by right and left side portions. One or two side portions may be provided that pivot on a shaft. The shift mechanism may be a spring that is mounted on the shaft for biasing the side portion toward the second position.
According to yet another aspect of the invention, the trigger may be a hook that is mounted on a slide that is secured to the headrest pad. A torsion spring may be secured between the hook and the slide. The hook is displaced when the impact exerts an inertial load to the headrest pad above a predetermined level.
Another feature of the invention is that the headrest pad may have right and left side portions that pivot independently relative to each other. The headrest pad may have a central section that is flanked by right and left side portions that are shifted fore and aft in a linear direction independently relative to the central section. A ratchet connection may be provided between the side portion or portions and the headrest pad that permits the side portion or portions to be locked in one of a plurality of angular positions relative to the headrest body. The trigger may be a hook that is mounted on a slide secured to the headrest pad with a torsion spring being secured between the hook and the slide. The hook may be displaced when an impact exerts an inertial load to the headrest pad above a predetermined level and wherein the torsion spring exerts a force on the shift mechanism that locks the side portion in one of the angular positions.
Other aspects of the invention will be better understood in view of the attached drawings and following detailed description of the invention.